1.索引失效原因
1.全值匹配
2.最佳左前缀法则
2.Orcale自增ID
CREATE TABLE testTable1
(
ID INT NOT NULL,
NAME VARCHAR2(4000) NOT NULL,
PRIMARY KEY(ID)
);
-- 创建序列
CREATE SEQUENCE te11stTable1_ID_SEQ MINVALUE 1 NOMAXVALUE INCREMENT BY 1 START WITH 1 NOCACHE;
-- 创建触发器
CREATE OR REPLACE TRIGGER testTable1_INS_TRG BEFORE INSERT ON testTable1 FOR EACH ROW WHEN(NEW.ID IS NULL)
BEGIN
SELECT testTable1_ID_SEQ.NEXTVAL INTO :NEW.ID FROM DUAL;
END;
3.Oracle去重复
SELECT DISTINCT asn.MCID FROM MVVW_ASN asn where asn.MCID is not null
